Textile mat for industrial use in the field of civil engineering

ABSTRACT

A FABRIC MAT FOR SOIL STABILIZATION HAS CONTINUOUS BANDS OF SINGLE PLY FABRIC ALTERNATING WITH INTERVENING CONTINUOUS BANDS OF TWO-PLY FABRIC FORMING BETWEEN THE TWO PILES CONTINUOUS HOLLOW TUBELIKE CONTAINERS WHICH ARE FILLED WITH SAND, GRAVEL OR THE LIKE. ONE END OF THE TUBELIKE CONTAINERS IS CLOSED BEFORE FILLING AND THE OTHER AFTER FILLING. THE MATS MAY HAVE SELVAGES ALONG OPPOSITE SIDE EDGES WHICH ARE SECURED TO SELVAGES OF LIKE MATS TO CONNECT A PLURALITY OF MATS TOGETHER.

Feb. 9, `1971 f MAsAzuMl N'lsHlzAwA ETAL 3,561,219

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' TEXTILE MAT FGR INDUSTRIAL USE IN THE FIELD OF CIVIL ENGINEERING Filed April 1o, 196e L esheets-sneet Fel 9, 1971 MAsAzUMl NlsHlzAwA ET AL TEXTILE MAI Eon INDUSTRIAL usE IN THE FIELD 0E' cIvIL ENGINEERING Filed April 10,' 1968 6 Sheets-Sheet 5 Pfg.

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TEXTILE MAT FOR I Filed April 1b. 1968 NDUSTRIAL USE IN THE FIELD 0F CIVIL ENGINEERING I e sheets-sheet es United States Patent O 3,561,219 TEXTILE MAT FOR INDUSTRIAL USE IN THE FIELD F CIVIL ENGINEERING Masazumi Nishizawa and Kaizo Kotera, Otsu-shi, and Michitsura Ohta, Takatsuki-shi, Japan, assignors to Toray Industries, Inc., Tokyo, Japan, a company of Japan Filed Apr. 10, 1968, Ser. No. 720,234 Claims priority, application Japan, Oct. 13, 1967, 42/ 86,482; Dec. 18, 1967, 42/ 105,514 Int. Cl. E021) 3/12 U.S. 'Cl. 61-38 9 Claims ABSTRACT OF THE DISCLOSURE A fabric mat for soil stabilization has continuous bands of single ply fabric alternating with intervening continuous bands of two-ply fabric forming between the two plies continuous hollow tubelike containers which are filled with sand, gravel or the like. One end of the tubelike containers is closed before filling and the other after filling. The mats may have selvages along opposite side edges which are secured to selvages of like mats to connect a plurality of mats together.

The present invention relates to a textile mat for industrial use in the field of civil engineering, more particularly to a woven mat provided with a plurality of hollowed portions for containing sand or gravel and which can be used as a material for reclamation in the field of civil engineering.

Generally, concrete blocks, asphalt-mats, wood blocks, stones, etc., have been used as materials for reclamation of bank-revetment or coast protection works. However, these materials are not economical because of the cost of their transportation. The quality of these is also unsatisfactory from the point of view of working efficiency and mechanical properties. It is already known that sand bags or some textile mat comprising a plurality of sand bags connected to each other by sewing them with threads are used now and then. Similar drawbacks as described above are also present in case of sand bags and even in case of using textile mat comprising a plurality of sand bags, it is difficult to carry out the work with high efficiency, and further there is a tendency of the connected portion of the sand bags breaking.

The principal object of the present invention is to provide a practical woven mat having a plurality of hollowed portions for containing sand or gravel which can be used as a material for reclamation in the field of civil engineering. v

Another object of the present invention is to make possible economical reclamation by using a textile mat of the invention in the same field.

Further object of the present invention is to make reclamation work easy by using a textile mat of the invention in the same field.

Generally, the textile mat of the present invention comprises a plurality of hollowed portions consisting of hollowed cloth, and a plurality of connecting portions between the hollowed portions without using any connecting sewing threads.

The hollowed portions are arranged in a parallel condition to each other, further, it is preferable to close M1ce one end of the hollowed portions of the textile mat of the invention before using as a material for reclamation.

The textile mat of the present invention can be easily manufactured by power looms but it is necessary to have some particular design of the Iwoven cloth for the present purpose and also consideration must be given regarding selection of the textile yarns for manufacturing the textile mat of the invention.

The textile mat of the invention (hereinafter called the woven mat) is lled with sand or gravel by pouring a slurry composed of `water and insoluble matters such as sand, gravel, etc., into its hollowed portions, while water passes through the numerous line intervened spaces between the textile yarns of the woven mat (hereinafter called mes Consequently, it is very easy to make a compact material of sand or gravel for reclamation in the field of the civil engineering. The above-mentioned operative character of the woven-mat of the invention is one of its remarkable features.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which,

FIG. 1 is a perspective view of an embodiment of the woven mat according to the invention,

FIG. 2 is an enlarged view of the cross section of the hollowed portion of the woven mat shown in FIG. 1,

FIG. 3 is an enlarged plan view of the hollowed portion of the woven mat shown in FIG. 1,

FIG. 4 is an explanatory diagram for showing the relation between the accumulated frequency in percent and particle size in mm. of sand contained in an experimental slurry poured into the woven mat according to the invention,

FIGS. 5 and 6 are diagrams of results obtained by experiments for showing the relation between the size of fine spaces existing in the woven mat and the maximum particle size of sand which passes through the spaces when slurry containing water and sand is poured into a hollow portion of the woven mat of the invention,

FIG. 7 is a perspective view of another embodiment of the woven mat provided Iwith a plurality of hollow portions having particular yarn density, according to the invention,

FIG. 8 is an enlarged plan view of the woven mat shown in FIG. 7,

FIG. 9 is a plan view of another embodiment of the woven mat of the invention,

FIG. l0 is an explanatory section view, taken along line X-X in FIG. 9,

FIG. ll is an explanatory drawing for showing the variable yarn density of the hollow portion of another embodiment of the woven mat, according to the invention,

FIG. l2 is also an explanatory perspective view of the woven mat provided with reinforced edge portion, according to the invention,

FIG. 13 is an explanatory skeleton sketch showing a method for carrying the woven mat of the invention which is filled with sand or gravel,

FIGS. 14 and l5 are explanatory diagrams showing examples of end uses of the woven mat according to the invention.

Referring to FIGS. 1 and 2, an embodiment of the woven mat of the invention is composed of a plurality of portions 1 having so-called hollow-cloth structure and a plurality of intervened portions 2 between the adjacent portions 1. The intervened portions 2 form a single sheet, and these portions 1 and 2 are arranged in a parallel condition to each other. In the above-mentioned embodiment, the portions 1 and 2 may extend along the warp yarn or weft yarn of the woven mat of the invention, for instance, if the hollowed portions 1 extend along the weft yarn 4, the direction of the hollowed portions 1 is perendicular to the direction of the warp yarn 3, as shown in FIGS. 1 and 2.

To obtain sufficient strength of the woven mat for practical use, it is necessary to utilize synthetic fiber materials in the form of multifilament yarn with or without twist, or spun yarn, or a tape yarn composed of film, and/or a monotilament yarn. However, it is also possible to use union yarn or blended spun yarn mainly composed of synthetic fiber materials together with other textile fiber material such as cotton, jute, etc., as the other component. The synthetic ber material of the woven mat prevents decomposition of the woven mat in water or earth. To reinforce the resistance of the synthetic ber materials of the woven mat, some chemical agent for improving the resistance of the synthetic fiber material to ultraviolet rays or abrasion, may be used for coating the woven mat in such a way that the porosity of the woven mat is maintained. For example, synthetic resin such as acrylic, vinyl chloride or polyamide resin or bituminous agent can be used for the above-mentioned purpose.

The conventional synthetic fiber materials such as polyester, polyamide, polyacrylic, polyvinyl and polyolefine fiber materials can be used for manufacturing the woven mat of the present invention. However, synthetic fiber materials having high tenacity and high resistance against alkali and containing some stabilizer against ultraviolet rays is preferably used for the present purpose.

As already illustrated, a slurry composed of water and sand or gravel is poured into the hollowed portions of the woven mat of the invention when the material for reclamation is made by using a suitable mechanical means such as a pump. The efficiency of the above-mentioned lling operation mainly depends on the porosity of the woven mat, in other words, if the size of the unit mesh of the woven mat is so large that a large quantity of sand passes through the woven mat together with water or if the size of the unit mesh of the woven mat is so small that it becomes difficult for water to pass without application of a higher pressure, the working efficiency s lowered. Experiments were performed in order to nd the most preferable unit size of the mesh. Referring to FIG. 3, experimental fabrics made of synthetic multifilament yarn having equal density of warp 3 and weft 4 yarn were prepared. The size of the unit mesh S is presented by an intervened space beween the adjacent warp yarn 3 and is designated by a in FIG. 3. An experimental slurry composed of water and sand is poured on the cloth.

The particle size of the sand contained in the experimental slurry varies and the amount of the sand having different gain size also varies as shown in FIG. 4, wherein the ordinate represents the accumulated frequency in percent and the abscissa represents the particle size of the sand contained in the slurry, where the particle size of the sand is represented by the minimum thickness of the respective particles of sand.

Table 1 shows the structure of experimental test pieces having different meshes. The text was performed under the following condition: Composition of slurry usedwater 70%, sand 30%. Vacuumcorresponds to 50 cm. water column.

TABLE 1 Size of unit Structure of test piece mesh (a) in mm.

Number 0i test piece:

860 denier x 860 denier 1 WWB/,uch 0.40 x 0.40 (0.40)

1 000 x 1,000 2 mm 0.31 x 0.31 (0.31)

840 denier/1 x 840 denier/l 26ends/inuh X 26Icks/inoh 1,260 denier x 1,260 denier mende/inch x 241ieks/inch 840 denier/1 x 84o denier/1 ggendrlinch X 33pm/inch 840 denier/ 1 x 840 denier/1 38mm/inch X 14pm/inch 70 denier x 70 denier goeudu/mh X gnam/inch Referring to FIG. 4 wherein the abscissa represents the size (a) of the unit mesh of the woven mat and the ordinate represents the maximum particle size of the sand which passes through the unit mesh, respectively, it was noticed that the size (a) of the unit mesh is limited to three times the particle size of the sand which is desired for accumulation on the woven mat.

Generally, the filling of sand or gravel in the hollowed portions of the woven mat of the invention is carried out under a reduced pressure using a vacuum pump in the range of 50 cm. to 200 cm. water column, therefore the maximum particle size of the sand which can pass through the mesh of the woven mat varies in accordance with the vacuum condition of the pump. The result obtained by our further experimental test carried out under the vacuum of 200 cm. Water column is shown in Table 2, where R, represents the accumulated amount of sand in percent calculated by the following definition, that is R=amount of sand accumulated on the test piece/amount of sand supplied in percent, T represents the time for completion of the filtration of the slurry poured on the test piece, and M represents the maximum particle size of the sand which passes through the woven mat in mm.

It was found from the result obtained as shown in Table 2, that the size (a) of the unit mesh is limited to 1.5 times the particle size of the sand which is desired to be accumulated on the woven mat.

Further experimental test was performed under a working condition similar to the actual filling operation of sand into the hollowed portion of the woven mat. That is, several pieces of bags made of Woven cloth composed of polyamide multifilament yarn of 1,260 denier were used. The structure of the test pieces was plain weave, the size of the unit mesh of the test pieces were designed as shown in Table 3, and the size of the bag was 30 cm. in diameter and 10 m. in length. A slurry composed of water (70%) and sand (30%) was poured into the respective bags for 40 minutes at a pouring speed of 1.00 liter per second, and the amount of sand accumulated in the bags was measured. The particle size of the sand contained in the slurry varies as shown in FIG. 4. Table 3 shows the results obtained by the above-mentioned test, where X represents size of unit mesh a/particle size of sand which is desired to be accumulated in the bag, Rt represents amount of sand accumulated in the bag/ amount of sand supplied to the bag in percent, when a slurry composed of water and sand with a theoretical mixing ratio of 72 and 28 percent.

TABLE 3 Amount of sand Size of accumulated Apparent condition unit mesh in the of filling operation X (a) in mm. bag in m3 Rt; of sand into the bag 0. 015 0. 23 32. 3 Overilows from the mouth of the bag. O. 030 0. 33 46. 1 Do. 0. 060 0. 49 67. Do. 0. 090 0. 62 86. l Good. 0. 120 O. 63 87. 5 D0. 0.150 0. 59 82. 3 Do. 0. 180 0.58 80.6 D0. O. 210 50 69. 5 Water containing sand passes through the bag. 0.240 O. 20. 4 Do.

Consequently, when it is desired to accumulate sand characterized by the lower limit of particle size of up to at least 0.06 mm., it was found that the size of the unit mesh of the woven mat from 0.09 mm. to 0.18 mm., that is, 1.5 to 3.0 times the particle size of the sand, must be chosen, from the experimental test shown in Table 3.

After the slurry has been poured into the hollowed portions of the woven mat of the invention, the opened end portions of the woven mat are closed by a suitable method such as stitching with threads, etc., and then carried to the 'work site by some mechanical means. The sand or gravel contained in the woven mat of the invention sometimes contain water, therefore, it is necessary to use woven yarns having sufficient strength to prevent breakage of the woven mat while carrying it.

The thickness of the yarn for manufacturing the woven mat of the invention must be chosen so as to conform with requirements which can be decided from the required mechanical properties such as tensile strength and abrasion resistance, filtration, etc. For example, it is preferable for the tensile `strength of the woven mat to be more than 100 kg./cm., and the thickness of the single woven yarn more than 200 denier. Further, when multifilament synthetic yarn is used, it is further preferable to twist the yarn from 0 to 400 turns per meter to improve the resistance to abrasion. It may also be used as doubled yarn or twine rope yarn for the material for the woven mat of the invention. The size of the woven mat varies in accordance to the practical end use. From our experimental test, it was found that a woven mat of m. x 20 m. filled with sand is preferable for reclaiming in the field of the civil engineering. f

In our practical test of the woven mat of the present invention, it was observed that relative slip between the warp and weft yarns occurred when the slurry was being poured into the hollowed portions 2, thereby the size of the mesh of the woven mat is varied. The above-mentioned slip between the warp and weft yarns must be avoided in order to maintain a uniform working condition during the filling operation of sand or gravel into the woven mat of the invention. t

The above-mentioned slip between the warp yarns and the weft yarns of the woven mat can be prevented by fixing the crossing of the warp yarns with the weft yarn.

The fixing of the crossing of the Warp yarns with the weft yarns can be carried out by the so-called heat-set treatment of the woven-mat, or fixing the crossed portions of the warp yarn with the weft yarns of the woven mat by a certain synthetic bonding agent. Further, the above-mentioned slip between the warp yarn and the weft yarn can also be prevented by using a particular structure of the woven mat.

In FIGS. 7 and 8, embodiments of the woven mat provided with particular woven structure are shown. In the drawing of FIG, 7, the woven mat comprises holA lowed portions 1 composed of hollowed cloth and connecting portions 2 between the adjacent hollowed portions 1. The warp density of the connecting portions 2 and of the side portions 1 of the hollowed portions 1 are more dense than the main portion of the hollowed portions 1. It was observed that when the warp density of the connecting portions 2 and of the side portions 1' is 1.2 times larger than the main portion of the hollowed portions 1, slip between the warp yarns 3 and weft yarns 4 can be eectively prevented, and a width of the connecting portions 2 of 2 cm. was effective for the present purpose.

From the practical point of view, it is desirable to have the length of the hollowed portion of the woven mat of the invention more than 5 meters. In this case, it is better to use a woven structure of woven mat comprising a plurality of hollow cloth wherein the hollowed portion extend in the direction of the warp yarn and a plurality of connecting portions between the adjacent hollowed portions. Consequently, it is clear that there is certain limitation to the number of hollowed portion of the woven mat manufactured by a power loom (hereinafter called the unit woven mat), in other words, if it is required to supply woven mat having a certain number of hollowed portions which is larger than the number of hollowed portion of unit woven mat manufactured with a power loom, the woven mat is manufactured by connecting a plurality of the unit woven mats by sewing them together. The woven mat formed by combing a plurality of unit woven mats is hereinafter called a combined woven mat.

It was also disclosed that, when the combined woven mat is used for filling sand or gravel, warp yarns, particularly the warp yarns of the connecting portions between th adjacent unit woven mats frequently slide on the weft yarns by lateral force caused by filling of sand or gravel into the hollowed portions of the woven mat.

In other words, the mesh of the hollowed portions of the woven mat become enlarged, thereby the filling efficiency of sand contained in the slurry poured into the hollowed portions was reduced. To prevent the abovementioned drawback of the combined woven mat, a certain woven structure of the woven mat was disclosed. Referring to FIGS. 9 and 10, the unit woven mat of an embodiment of the invention comprises a pair of hollowed portions 1 and connecting portion 2 between the hollowed portions 1 and a pair of selvage 8. The woven structure of the selvage 8 is different from the other portions of the unit woven mat for example in FIG. l0, weft yarns 12, 15, 16 19, 20 are interlaced with the warp yarns 9 of the selvage y8 while weft yarns 13, 14, 17 and 18 are not interlaced with the warp yarns 9` of the selvage 8, on the other hand weft yarns 12, 13, 16 and 17 are interlaced with warp yarns 10 of the selvage 8 while weft yarns 14, 15, 18 and 19 are not interlaced with the warp yarns 10 of the selvage 8. As mentioned above, there are two kinds of weft yarns, one interlaces with the warp yarns of the selvage while the other do not interlace. The order of picks of the interlacing of the weft yarn with the warp yarn of the selvage may be designed in any desired manner. The width of the selvage is preferably 10-30' mm. By the above-mentioned particular woven structure, slippage of the warp yarns of the selvage and the side portion of the hollow cloth of the woven mat on the weft yarns can be prevented when filling sand or gravel into the hollowed portion of the woven mat. It is preferable to apply the particular structure shown in FIG. 8 wherein the density of warp yarns in the connected portion 2 and the side portion of the hollowed portion 1 of the woven mat is larger than the 7 other portions, to obtain further prevention of slip between warp yarns and weft yarns.

Referring to FIG. 1l, a modified embodiment of the woven mat of the invention is shown. The woven mat of this embodiment comprises a woven structure similar to the woven mat shown in FIG. 1 except for the variation of the density of the weft yarn in the hollowed portion 1. The density of the weft yarn in the hollowed portion 1 varies with three groups, that is, supposing one end of the hollowed portions 1 are closed by a suitable means, and the portions including the closed end of the hollowed portions 1 are called the third portions 7, and the portions including the opened end of the hollowed portions 1 are called the first portions 5, and the portions between the first and the third portions are called the second portions `6, the density of the weft yarn is increased from the first portion to the third portion, in other words, the density of the weft yarn in the first portion is the lowest, while that of the third portion is the highest. It was also disclosed that the efficiency for filling sand, gravel into the hollowed portions of the woven mat was remarkably improved by using the abovementioned modified embodiment of the woven mat, as shown in the following example.

EXAMPLE 1 A standard bag was made with a plain weave cloth of warp yarn 840 denier, weft yarn 840 denier, warp density l/cm. weft density 15/cm. The size of the bag was 30 cm. diameter x 10 m. length. A test bag according to the invention was made with a woven hollow cloth of warp yarn 840 denier and weft yarn 840 denier. The size of the test bag was the same as the standard bag. The yarn density of the woven hollow cloth was designed as follows; in the first portion of 3.3 m. in length warp cm. x weft l2/cm.; in the second portion 3.3 m. in length warp l5/cm. x weft l5/cm.; in the third portion of 3.4 m. in length, warp l5/cm. X weft lf3/cm. Both bags were disposed at an inclination of 30. The opened mouth was on the top. A slurry composed of water (50%) and sand (50%) was poured into the opened mouth of the bags at a supplying rate of 0.2 m per minute with a sand pump, and the time required for filling the bag was measured. The time required for filling the standard bag was 8 minutes, while the time for the modified bag of the invention was 5 minutes. As shown in the abovementioned experimental test, the efficiency for filling sand into the bag was remarkably improved by using the above-mentioned bag according to the invention.

After completion of filling sand or gravel into the hollowed portions of the woven mat of the invention, the open end portion 11 of the hollowed portions 1 is firmly closed by a certain way such as sewing by threads or by strands, and then carried to the work site. However, the woven mat filled with sand or gravel was frequently broken at the connected portions 2 while carrying because both sides of the connected portions 2 receive unexpected lateral load caused by shock or excess weight of sand or gravel containing water. Consequently, when the sides of the connecting portions 2 is broken, the woven structure of the hollowed portions is broken and the sand or gravel filled in the hollowed portions fiows out. To prevent the above-mentioned trouble, it is desirable to reinforce the side of the connecting portions 2. One method for reinforcing the side of the connecting portions 2 is shown in FIG. 12, wherein the side portion 21 of the connecting portion 2 is cut and the cut portions are folded and sewn by thread 22. A piece of cloth 23 is attached to an inside end of the cut portion 21 by sewing to the connecting portion 1 as shown in the drawing. By this method of reinforcing the side of the connecting portions 2, the above-mentioned possibility of breaking the side of the connecting portions 2 can be completely prevented. Instead of attaching a piece of cloth 22 for reinforcing, a certain synthetic resin may be used for reinforcing the side .end portion or the connecting portions 2 of the woven mat by the coating method.

In FIGS. 13, 14 and 15, examples of using and carrying the woven mat of the invention are shown, The woven mat 23 filled with sand or gravel is attached with a plurality of hanging ropes 25 and lifted by a hanger 26 of a conventional crane 27 installed on a base 28, and transported to the site in the water 29. Therefore, it is very easy to perform the reclamation work by using the woven mat according to the invention with high working efiiciency and at low cost. The woven mat 23 filled with sand or gravel according to the invention has a flexible construction, consequently the woven mat 23 filled with sand or gravel conforms very well to the irregular surface of the ground 30 or 31 and a construction block 32 can be stably set on the woven mat 23, as shown in FIGS. 14 and l5.

What is claimed is:

1. A fabric mat for soil stabilization comprising alternating continuous bands of single ply fabric and intervening continuous bands of two-ply fabric forming between said two plies continuous hollow tubelike containers for sand, gravel or like material, said continuous bands of single ply fabric joining said bands of two-ply fabric and bounding said tubelike containers along opposite longitudinally extending sides, and means closing one end of said tubelike containers along one boundary of said fabric mat, said fabric being formed of strands of at least mainly synthetic material, said two-ply bands being of mesh fabric with a mesh size to permit passage of water while retaining said sand, gravel or like material, interlacing portions of said strands of said mesh fabric being fixed to each other to maintain the mesh size of said fabric substantially constant, said bands of single ply fabric between said tubelke containers being centrally split in a lengthwise direction for a selected length at the open ends of said tubelike containers and the resulting edges being reinforced.

2. A fabric mat according to claim 1, in which the density of strands extending in a lengthwise direction in said bands of single ply fabric and in adjacent portions of said bands of two-ply fabric is at least 1.2 times greater than in the remaining portions of said bands of two-ply fabric.

3. A fabric mat according to claim 1, in which the mesh size of said two-ply fabric is from 1.5 to 3 times the granular size of material to be filled in said tubelike containers.

4. A fabric mat according to claim 1, in which said fabric is woven and said bands extend in a warp direction, said mat further having a part of opposite selvages extending in a warp direction.

5. A fabric mat according to claim 4, in which weft strands of said fabric interlace with warp strands in said selvages once in two successive picks.

6. A plurality of fabric mats according to claim 4, in which said mats are connected together at said selvages.

7. A fabric mat for soil stabilization comprising alternating continuous bands of single ply fabric and intervening continuous bands of two-ply fabric forming between said two plies continuous hollow tubelike containers for sand, gravel or like material, said continuous bands of single ply fabric joining said bands of two-ply fabric and bounding said tubelike containers along opposite longitudinally extending sides, and means closing one end of said tubelike containers along one boundary of said fabric mat, said fabric being formed of strands of at least mainly synthetic material, said two-ply bands being of mesh fabric with a mesh size to permit passage of water while retaining said sand, gravel or like material, interlacing portions of said strands of said mesh fabric being fixed to each other to maintain the mesh size of said fabric substantially constant, said fabric being woven and the density of strands perpendicular to said hollow tubelike containers varying in a direction lengthwise of said containers, being greatest at the closed ends of said containers and least at the open ends of said containers.

8. A fabric mat according to claim '7, in which said bands of single ply fabric have reinforced portions in the vicinity of the open ends of said tubelike containers.

9. A fabric mat for soil stabilization comprising a unitary continuous fabric having spaced parallel bands of constant width in which said fabric is of two-ply construction and intervening narrower bands of constant width in which said fabric is of single ply construction, said bands of two-ply construction extending the full Width of the fabric and forming continuous hollow tubelike containers of uniform width for sand, gravel or the like joined with one another by said bands of single ply construction, and means joining the opposite plies of said bands of two-ply construction to close one end of said tubelike containers along one boundary of said mat, said fabric being formed of strands of at least mainly synthetic material, the fabric in said bands of two-ply construction being open mesh fabric with a mesh size to permit passage of water while retaining sand, gravel or like material, crossing portions of said strands of said mesh fabric being fixed to each other to maintain the mesh size of said fabric substantially constant and the fabric in said bands of single ply construction being stronger and denser than the fabric in said bands of two-ply construction.

References Cited UNITED STATES PATENTS 2,471,380 5 1949 Wallwork 139-3 89X 752,637 2/1904 Mankedick 61-38 3,374,635 3/1968 Crandall 61-38 3,396,542 8/1968 Lamberton 61-38 3,425,228 2/1969 Lamberton 61-38 DAVID I. WILLIAMOWSKY, Primary Examiner P. C. KANNAN, Assistant Examiner 

